In recent years, for mobile electronic devices such as a cellular phone or a PDA using liquid display device, organic EL display device or the like, further size and weight reduction are desired. Accordingly, there is a trend for a smaller region around display area, i.e. narrower frame region, and vigorous development of such is underway.
For thickness and cost reduction, there is an increased trend for display devices provided with a full monolithic type circuit substrate having a peripheral circuit necessary for driving, such as a driver circuit. In a display device provided with a full monolithic type circuit substrate, a circuit for driving the pixels is formed on the circuit substrate. As a result, a part of the area of the circuit substrate that is not a display region (frame region) increases. Therefore, development for a narrower frame is underway.
In a conventional display device, low resistance aluminum is used for wiring inside a panel. When this wiring is extended to the panel exterior to be used as an external connection terminal, an exposed part of the aluminum film can become corroded. To address this problem, a measure was taken in which the aluminum film used for the wiring inside the panel is connected to a separate metal film disposed in a lower layer below the aluminum film inside the panel, and the metal film is used to connect the wiring inside the panel to the panel exterior (see Patent Document 1, for example).
In Patent Document 1, a configuration which prevents corrosion of an external connection terminal is also disclosed. In this configuration, an aluminum film is used as a wiring inside the panel and the aluminum film is extended to the panel exterior to be used as an external connection terminal. An exposed portion of the aluminum film extended to the panel exterior is covered with a chrome (Cr) film and an indium tin oxide (ITO) film.